Use Dividers for Quick & Easy Dovetail Layout – No Measuring

I’m in the midst of making a place to put my woodworking stuff, a la Christopher Schwarz’s “The Anarchist’s Tool Chest.” The picture at left shows my dire need for just such a receptacle. (And it perhaps also shows a need to cull my collection.)

It’s the same chest build Chris is teaching to a full house of students right now at Roy Underhill‘s The Woodwright’s School in Pittsboro, N.C., and although we started on the same day, as Chris’s blog reveals, the students are well ahead of me. (I’m guessing they’ve had fewer meetings to attend in the last few days.)

This chest, when finished, will be painted on the exterior (likely a slate blue – which will surprise exactly no one who knows me), so the dovetail joinery won’t show. And, I want it to look sturdy and rugged (and actually be sturdy and rugged). So I elected to lay out big tails and fairly big pins rather than fuss around with delicate and refined.

I’m gang-cutting the tails (which is why I’m going tails-first on this one) because even though they’re large, there are still a lot of them. I might even be brave enough to “gang cope” the majority of the waste before separating the two tailboards for chopping. Maybe.

But no matter what size tails you like, I think it’s easiest to lay them out using two sets of dividers – it’s a lot faster and simpler than measuring the layout on all four ends of the tailboards. Plus, as long as you don’t adjust either set of dividers after you’ve determined the spacing, all of your dovetail layout will match perfectly (something that’s a challenge to achieve when using a tape measure or rule). I make no promises, however, about perfection once the sawing starts.

I used a pencil to mark the tails, because I find it’s a waste of time to bother knifing in whichever part of the joint you choose to cut first. When I transfer to the pin board, then I’ll grab my marking knife.

While we’ve written about this dovetail layout method several times over the years, until I actually saw it done, I didn’t really get it. So I’ve filmed a short video to show the method. Apologies for the several title cards and words. I was planning a voice over, but one of the cats kept meowing in the background (they love to play in the shavings pile when I’m in my shop/study). So instead, you get guitar music (because I’m not cool enough for the banjo).

And…I’ve shot another (longer) video. I’m calling this one “the director’s cut,” because everything is in it, soup to nuts (as Chris would say). Nothing on the metaphorical cutting-room floor. Might want to grab a cup of tea first.

I watched the videos this morning as I was just about to mark out a set of dovetails for a project. It took a couple of watches to get the concept before it finally clicked. The “director’s cut” video really helped. Thanks! And yes, I was late for work this morning.

Megan: Thanks again for the videos. I preferred the Director’s Cut as the directions were clear. The shorter video confused me on the starting and ending points as the left half-tail was blocked from view so I couldn’t see where you started the second set of dividers. No matter as the longer video showed quite clearly how to do this.

Megan,
Thank you for this video. I had a whole bunch of kitchen cabinet drawers to make and this video cleared up the concept better than a thousand words. After building the Anarchist’s tool chest and a couple other boxes the actual cutting of dovetails is becoming reasonably routine and accurate but laying them out has remained a puzzlement. Your video really made it easy and it made it easy to vary the ratios to get narrow pins or more or less tails. Next step will be to control the pin width to match my paring chisel.

Consider this next time. Gang-up both the front and back pieces of your chest in your vice. Run through your layout process for both boards as you did for the one shown. Now flip one board end for end, keeping the tops together, and use the marks from the one end and extend them to the other end. Flip the other and extend your layout to the fourth edge. You will now have the four boards marked out in less than half the time you were going to take – and all four layouts should match. Now cut both boards together at one time. You have just cut tails for one end of your chest in a little more time than it would take you to cut one set of tails on one piece. Flip both boards, keeping the tops together, and cut the other ends. This whole process will cut your time spent cutting tails in about half. Layout and cutting or your pins will still take about the same amount of time, but I think you will see more regularity or consistancy in both your tails and pins.

This activated my inner geek. I think I figured out how to set the second divider. Decide how many tails you want (N) and the desired pin width (W). Mark the arbitrary half pins at each end. Then measure between those marks (X). Set the second divider to: X/N + W/N.

As an armchair observer and semi-perfectionist, I have the following nit to pick:
When using the dovetail gauge to mark a line, first put the pencil in the hole, then move the gauge to the pencil. That will eliminate the tiny registration error that happens when you align the marking gauge to the hole by eye.
It also demonstrates the tiny bit of improved accuracy you get with divider instead of pencil.
Nice video, Megan.

Your are, of course, correct – and typically, I’ll drop my marking knife in the pin hole then move my DT gauge against it. But the knife lines don’t show up too well in video. (And one could argue that a slight variation adds to the hand-cut look…but this one won’t, because it’s bourbon time!)